Harnessing the human monocyte system to improve surgical recovery Over 30 million patients undergo a major surgery annually in the US. Patients? recovery after surgery is highly variable and can be severely compromised by complications, such as infections, prolonged pain, and functional impairment. However, our current approaches to predict a patient?s recovery are anchored in clinical and phenotypical data and perform poorly. Surgical injury produces a multi-cellular immune response that, when dysregulated, leads to adverse surgical outcomes. Examining the human immune system in depth, in patients undergoing surgery is a logical and promising strategy to identify biological signatures for risk prediction and to reveal mechanisms that can be exploited to improve surgical recovery. Our research program utilizes the high-dimensional immune monitoring of patients undergoing surgery to identify modifiable immunological mechanisms that accurately predict a patient?s recovery. This MIRA proposal builds on our extensive translational research indicating that immune responses contained in the human Monocyte System (hMS) strongly correlate with pain resolution and functional recovery after major joint replacement surgery. We will pursue three inter-related, but non-overlapping goals focusing on the hMS: First, we will assess the phenotypic and functional dynamics of circulating monocytes in response to surgery to determine the role of the hMS in the pathobiology of surgical recovery. Second, we will interrogate the hMS before surgery to determine whether patients? pre-surgical immune states determine the course of surgical recovery. Third, we will use a reverse translational strategy using a pre-clinical mouse model of surgery to test whether ?druggable? immunological targets identified in humans can accelerate recovery. We will use the following innovative and multidisciplinary strategies: 1) high-dimensional profiling of the hMS in response to surgery using single-cell mass cytometry (including dynamic alterations in cell phenotype, homing properties and effector responses); 2) identification of cellular, epigenetic and proteomic elements of a patient?s hMS, using an integrative analytical pipeline developed by our group; 3) evaluation of new targets for selective modulation of monocyte signaling responses in a mouse model that recapitulates hallmarks of the human immune response to surgery. A major strength of this proposal is the study of trauma-related immunology in a pertinent patient population by a clinician-scientist who has effectively pioneered high-content immune monitoring techniques at the bedside. The current program focuses on pain and functional impairment after orthopedic surgery. However, we will study fundamental mechanisms that are likely shared across many acute inflammatory conditions (e.g. other surgeries, blunt trauma or traumatic brain injuries). As such, we will be able to pivot towards the integration of our findings within the broader immunologic, metabolic, and neuro-hormonal responses to injury and the evaluation of other adverse outcomes after traumatic injury, such as infections, sepsis, or neuro-cognitive impairment.